Python re match case insensitive

How to Make Regular Expressions Case-Insensitive in Python — Ultimate Guide

Learn how to make regular expressions case-insensitive in Python with various methods such as re.IGNORECASE flag, (?i) syntax, and several functions. Improve your string matching capabilities now!

• Using the re.IGNORECASE Flag
• Using the (?i) Syntax in Legacy Python Versions
• PYTHON : Case insensitive regular expression without re.compile?
• Differences Between re.match() and re.search() Functions
• Using re.split() Function with re.IGNORECASE Flag
• Using re.sub() Function with IGNORECASE Flag
• Other code examples for making regular expressions case-insensitive in Python
• Conclusion
• Is Python re case sensitive?
• How do you ignore a case in re Python?
• Is there any difference between re match () and re search () in the Python re module?

Regular expressions are a powerful tool for string matching in Python. They allow users to search for patterns within text, and can be used for various tasks such as data validation, data cleaning, and data extraction. By default, regular expressions in python are case-sensitive. However, there are ways to make regular expressions case-insensitive. In this post, we will explore the various ways to make regular expressions case-insensitive in Python.

Using the re.IGNORECASE Flag

The re.IGNORECASE flag allows for case-insensitive matching of regular expressions in Python. This flag can be passed as an optional argument to re.compile() or as a parameter to search() , match() , or sub() functions. Here is an example:

import re# Case-sensitive search text = "Hello World" pattern = "world" match = re.search(pattern, text) print(match)# Case-insensitive search text = "Hello World" pattern = "world" match = re.search(pattern, text, re.IGNORECASE) print(match) 

As you can see, the first search with a case-sensitive pattern returned None , while the second search with the re.IGNORECASE flag returned a match object.

The re.IGNORECASE flag can also be used with the match() and sub() functions. Here are some examples:

import re# Case-insensitive match text = "Hello World" pattern = "hello" match = re.match(pattern, text, re.IGNORECASE) print(match)# Case-insensitive substitution text = "Hello World" pattern = "world" replace = "Python" new_text = re.sub(pattern, replace, text, flags=re.IGNORECASE) print(new_text) 

Using the (?i) Syntax in Legacy Python Versions

In legacy Python versions (Python 2 and earlier), the (?i) syntax can be used to turn on the “ignore case” flag for the entire expression. Here is an example:

import re# Case-insensitive search in legacy Python version text = "Hello World" pattern = "(?i)world" match = re.search(pattern, text) print(match) 

PYTHON : Case insensitive regular expression without re.compile?

PYTHON : Case insensitive regular expression without re.compile? [ Gift : Animated Search Duration: 1:11

Differences Between re.match() and re.search() Functions

The re.match() function searches only from the beginning of the string and returns a match object if found. On the other hand, the re.search() function searches through the entire string and returns a match object if found.

When using the re.IGNORECASE flag, it’s important to note that it affects both re.match() and re.search() functions. Here are some examples to illustrate the differences between re.match() and re.search() functions with and without the re.IGNORECASE flag:

import re# Case-sensitive match and search text = "Hello World" pattern = "Hello" match = re.match(pattern, text) search = re.search(pattern, text) print(match, search)# Case-insensitive match and search text = "Hello World" pattern = "hello" match = re.match(pattern, text, re.IGNORECASE) search = re.search(pattern, text, re.IGNORECASE) print(match, search) 

As you can see, when using a case-sensitive pattern, only the re.match() function returns a match object. However, when using a case-insensitive pattern with the re.IGNORECASE flag, both re.match() and re.search() functions return a match object.

Using re.split() Function with re.IGNORECASE Flag

The re.split() function can be used with the re.IGNORECASE flag to split a string while ignoring case. Here is an example:

import re# Case-insensitive split text = "Hello World" pattern = "o" new_text = re.split(pattern, text, flags=re.IGNORECASE) print(new_text) 

Using re.sub() Function with IGNORECASE Flag

The re.sub() function can be used with the IGNORECASE flag to perform case- insensitive string replacement . Here is an example:

import re# Case-insensitive substitution text = "Hello World" pattern = "world" replace = "Python" new_text = re.sub(pattern, replace, text, flags=re.IGNORECASE) print(new_text) 

Other code examples for making regular expressions case-insensitive in Python

In Python case in point, case insensitive replace python code sample

>>> import re >>> insensitive_hippo = re.compile(re.escape('hippo'), re.IGNORECASE) >>> insensitive_hippo.sub('giraffe', 'I want a hIPpo for my birthday') 'I want a giraffe for my birthday'

In Python as proof, how to make a string case insensitive in python code example

Conclusion

Making regular expressions case-insensitive in Python is important for flexible string matching. There are several ways to make regular expressions case-insensitive in Python, including using the re.IGNORECASE flag, (?i) syntax, and various functions with optional flags. By understanding these methods and best practices for using regular expressions, you can improve your string matching capabilities in Python.

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Case Insensitive Regex in Python

1. Case Insensitive Regex in Python
2. Match a String Using the Case Insensitive re.IGNORECASE Flag in Python
3. Match a String Using the Case Insensitive Marker (?i) in Python
4. Conclusion

Regular expressions match a particular string within a text in Python. They form a search pattern and check if this search pattern is present in the text or not.

In this article, we will be studying the case insensitive regex in Python. The different ways of performing the case insensitive searches in a text are explained further.

Case Insensitive Regex in Python

Search patterns are made up of a sequence of characters and can be specified using regex rules. However, to work with regular Python expressions, you first need to import the re module.

Case insensitive means that the text should be considered equal in lowercase and uppercase. We need to apply case-insensitive searches in our daily lives very often.

One such example is whenever we search for some commodity, say, a Bag . The information about the Bags will be displayed on the screen.

However, if we search bag in lower case letters or use mixed cases such as bAG , it should also display the same results. Therefore, we need to treat different case letters to be the same to search the results in specific scenarios easily.

Therefore, we use regular expressions which check the case insensitive patterns within a text.

So, let us discuss how to extract a search pattern from a text using regular expressions.

Match a String Using the Case Insensitive re.IGNORECASE Flag in Python

We can use the search() , match() , or sub() functions of Python to find whether our search pattern is present in the text or not and extract their exact positions.

• The pattern to be searched.
• The text in which the pattern is to be searched.
• A flag .

However, this flag parameter is an optional argument but is used to enable several features in Python.

The re.IGNORECASE is used as a flag to enable case insensitive searching within a text. It will consider the characters [A-Z] the same as [a-z] for a string.

Let us have an example of using the re.IGNORECASE as a flag in our code.

import re re.search('the', 'ThE', re.IGNORECASE) 

Similarly, you can pass the flag as re.IGNORECASE in the match() function or the sub() function to search for a case insensitive string in the text.

However, if you want to search for all the string occurrences in a text, you should use Python’s re.findall() function. It will find all the matched strings that are present in the text.

However, you must pass the flag re.IGNORECASE in the arguments to find the case insensitive strings in a text.

Let us see how to extract all the string occurrences within a text.

import re re.findall('the', 'The sources informed the police of tHe thieves.', re.IGNORECASE) 

The re.IGNORECASE flag, which is used above, can also be written as re.I . This re.I flag is also used to search a case insensitive pattern within a text.

Let us see it with an example.

import re re.findall('the', 'The sources informed the police of tHe thieves.', re.I) 

All these methods are present inside the re module in Python. Therefore, the re module must be imported into the program before using them.

Match a String Using the Case Insensitive Marker (?i) in Python

When you do not want to add the flag parameter in the search() or any other function to extract the string from the text, we use a case insensitive marker denoted by (?i) .

It is applied in the regex function before the search pattern without specifying an extra flag parameter.

Below is the code to use the case insensitive marker (?i) with the search() method.

import re re.search('(?i)TABLE', table) 

However, you can search the pattern within a much larger string and find all the multiple occurrences of the search pattern from the string using the findall() method in Python.

Below is the code snippet to use the case insensitive marker (?i) with the findall() method in Python.

import re text = "Let it rain, let it snow, let it do!" re.findall('(?i)LEt' , text) 

Therefore, the above code snippet outputs all the occurrences of the search pattern within the text. Put the symbol (?i) before the search pattern.

Conclusion

This article has discussed regular expressions and how to use them to find the case-insensitive search patterns within a text. We have used two ways.

First is the re.IGNORECASE flag, which is passed as an argument in the searching functions such as search() , match() , findall() , etc. You can also use the re.I flag to search for the case-insensitive patterns with your string.

However, the second method uses the case insensitive marker (?i) , placed before the search pattern in the searching functions.

We can find the case-insensitive patterns in our text using these methods.

Related Article — Python Regex

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